The Role of Electrostatic Networks in Ionic Liquids and its Molecular Mimics

Ionic liquids (ILs) are an important class of solvents often referred to as ‘designer solvents’ as their properties can be tuned by the structure of constituent ions. They show promise for applications in chemical synthesis, chemical separations, and the energy sector. However, widespread adoption depends on our ability to control and tailor their physical properties such as the dynamic viscosity. While it is now clear that the charged network plays a key role in governing ion and mass transport in ILs, the mechanism of how ion mobility (over picoseconds and nanometres) dictate bulk viscosity (over milliseconds and millimetres) remains unclear. This must involve long-range networks and structures that bridge the gap in time and length scales. The key challenge is to design a system, where the charged network can be fine-tuned without significantly altering other intermolecular interactions (e.g., hydrogen bonds and steric effects). This cannot be achieved by dilution by neutral additives such as water, or by changing the temperature. This experiment will study the molecular arrangement of a model IL, its isoelectronic molecular mimics, and their mixtures. This will provide insights into how the bulk liquid structure depends on the charged network while excluding confounding variables to the extent possible. This study will provide widely applicable key insights and form the basis for a subsequent study on the dynamics (e.g., backscattering, neutron spin echo spectroscopy).